(1) Field of the Invention
This invention relates to jacks and the like for lifting and lowering heavy loads. More specifically, this invention relates to a jack which incorporates a rack and pinon gearing system for lifting or lowering a vehicle or load.
(2) Prior Art
High Lift Jacks are well known as a means for lifting vehicles or other loads. Such jacks conventionally include an elongate toothed track (rack), a support base, a ratchet assembly operated by a handle, and a lift assembly which is attached to the load for lifting. Generally, the prior art jacks employ spring loaded pawls which limit the direction of travel of the lifting platform or assembly. In some instances, it has been known in the prior art to employ a pair of elongated racks with which a ratchet and pawl assembly cooperates to lift or lower a heavy object. Samples of such prior art devices are shown in U.S. Pat. No. 1,228,015 to Gates, et al., U.S. Pat. No. 444,427 to Edwards, U.S. Pat. No. 1,410,968 to Urquhart, and U.S. Pat. No. 189,468 to Johnson.
The Urquhart Gates, et al. and Johnson patents disclose jacks which include a pair of rack assemblies. In operation, the racks themselves are displaced relative to the ratchet and pawl assembly. This design characteristic tends to cause the jack to be quite complicated in manufacture, as is quite evident in the number of structural elements required to manufacture these jacks. Also this same design characteristic tends to contribute to instability of jack during use.
In regard to the Edwards device, the pair of rack members employed in his jack are stationary relative to its base and the ratchet and pawl system move up and down relative to the racks. The Edwards jack also employs a rack and pinion gearing system. However, in the Edwards jack, the gearing on the double racks functions only to catch the pawls which hold the lifting mechanism in place. The third rack which employs the rack and pinion system is only part of the lifting mechanism. The third rack functions in conjunction with the pinion only for the purpose of moving one portion of the lifting mechanism relative to the other, and does not mechanically interact directly with the double racks. Again, this system is very complicated and very expensive to manufacture. This system is also quite complicated and difficult to operate.
There therefore exists in the jack technology a need for a jack which can safely and easily lift heavy objects, and which will also remain stable during lifting. Further, there exists a need for a jack which has very few total parts so that it can be cheaply and easily manufactured. Finally, there exists a need for a jack which is very simple to operate.